Boss Battles:Boss battles would feature something of great significance to the story (usually :P)Like for example, one boss level could be named "Humanity's last stand" and the boss would be a giant satellite thing of UBER POWAFULNESS! ... Sorry had to. Anyways bosses would be huge (of course) and have a variety of attacks. Going back to the huge satellite thing example, it could shoot lasers, spawn laser ships to attack you, and try to suck in Grey Goo like a black hole. And the boss levels could have their own music.

Level Editor:The level editor would be a feature that could be unlocked after beating ether casual mode or timed mode. With this thing, you could...

>Make your own levels and share them>Add objects to your level for Grey Goo to eat>Set the level background, music, etc.>Create your own objects with their own behaviors (Like trees that shoot lasers ;D )

Switches:Switches would be a level mechanic in which if you activate one thing, it would trigger something to happen. You know :P

James(the maker of Tasty Planet) has stated previously that a level editor would be way too time-consuming and expensive. Also, their music is open source, so it would be hard to get unique music for bosses.